[Renal imaging and biopsy for diagnosis of renal masses]

Incidental diagnosis of renal tumors is more and more common. Imaging is of paramount importance for the caracterization of these tumors. Ultrasound allows the diagnosis of solid tumors, thereby excluding cysts. The gold standard is the CT-scan, the realisation of which must obey to precise quality criteria. MRI yields further informations in selected cases. Renal cancer is the main etiology, but benign tumors can be suspected in small tumors less than 4 cm. Angiomyolipoma and oncocytoma are the more frequent benign tumors. Angiolipoma can be diagnosed with CT-scan, but there are no radiological criteria for the diagnosis of oncocytoma. Renal percutaneous biopsy can be helpful in selected cases. It is recommended for bilateral tumors, or when a renal metastasis is suspected. For small lesions with radiological features consistent with the diagnosis of benign tumor, renal biopsy can confirm this diagnosis and lead surgical abstention. Nevertheless, few centers have a regular practise of renal biopsy. Its contribution is still to be evaluated.